Francis Galton imbued eugenics with a penchant for measuring all aspects of the human body. Galton relied heavily on the system for human physical measurements (anthropometry) developed by the French criminologist Alphonse Bertillon. Measurements of variation in human form provided much of the data upon which he and his student Karl Pearson developed modern statistics. American eugenicists hoped to use anthropometry to back up their claims about the superiority of the white race and people of northern/western European origin. Public schools, prisons, and mental hospitals all presented large "captive" populations to measure. Draftees into WWI provided a trove of data from which to determine the prototype (White) "American male" to compare to men of other races and ethnicities.
In most cases, it is not clear what point eugenicists were trying to make with their comparisons of body measurements. Apart from athletic prowess, no relationship has ever been shown between bodily measurements and intelligence or other behavioral attributes. Eugenicists also failed to take into account variables — such as differences in nutrition and health care — that could affect human development and account for differences between groups.
Intelligence tests took human measurement to new levels. In 1905, the French psychologist Alfred Binet developed a measure of "mental age" to help steer elementary students to academic or vocational tracks. Under this system, a child of average intelligence has a mental age equal to his chronological age. By 1910, Binet's mental age was used to generate an intelligence quotient or IQ (mental age/chronological age x 100). IQ scores range from 0 to 200 and fit a bell-shaped curve, with an average IQ of 100. Normal intelligence ranges from 86 to 115. Terms like "moron," "imbecile," and "idiot" described persons with IQs below 86, while "bright" and "genius" were used for scores above 115.
Eugenicists rapidly employed IQ or other intelligence tests to compare different racial and ethnic groups. These comparisons purportedly showed whites were more intelligent than blacks, native-born Americans were more intelligent than immigrants, and northern Europeans were more intelligent than southern Europeans. Educational psychologists believed IQ tests measured innate intelligence, but mostly they measured knowledge of white American culture and language. This underestimated the intelligence of new immigrants and disenfranchised Americans.